Quantum Fluctuations as the Origin of Laser Beam Filamentation
According to traditional theories, the filamentation1 of a laser beam as it passes through a nonlinear material is a consequence of the spatial growth2,3 of weak wavefront perturbations initially present on the beam. To a certain extent these perturbations can be removed by passing the beam through a spatial filter before it enters the medium. However, quantum fluctuations in the field amplitudes of the transverse side modes impose perturbations that cannot be removed by spatial filtering. These quantum fluctuations can lead to the filamentation of a beam with an otherwise perfect wavefront. We study the growth of these fluctuations and predict the nonlinear phase shift at which this process will become significant. We find that quantum-initiated filamentation imposes a fundamental limit to the intensities that can be propagated through a nonlinear material without beam breakup.
KeywordsNonlinear Material Quantum Fluctuation Side Mode Spatial Growth2 Nonlinear Phase Shift
- 1.V.I. Bespalov and V.I. Talanov, Filamentary structure of light beams in nonlinear liquids, JETP Lett. 3: 471 (1966)Google Scholar